64 lines
2.3 KiB
Python
64 lines
2.3 KiB
Python
"""Message wrapper with metadata support.
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This module defines a wrapper type that combines JSONRPCMessage with metadata
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to support transport-specific features like resumability.
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"""
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from collections.abc import Awaitable, Callable
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from dataclasses import dataclass
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from typing import Any
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from mcp_types import JSONRPCMessage, RequestId
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ResumptionToken = str
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ResumptionTokenUpdateCallback = Callable[[ResumptionToken], Awaitable[None]]
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# Callback type for closing SSE streams without terminating
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CloseSSEStreamCallback = Callable[[], Awaitable[None]]
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@dataclass
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class ClientMessageMetadata:
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"""Metadata specific to client messages."""
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resumption_token: ResumptionToken | None = None
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on_resumption_token_update: Callable[[ResumptionToken], Awaitable[None]] | None = None
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# Per-message HTTP headers (e.g. MCP-Protocol-Version, Mcp-Method) the transport should set.
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headers: dict[str, str] | None = None
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@dataclass
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class ServerMessageMetadata:
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"""Metadata specific to server messages."""
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related_request_id: RequestId | None = None
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# Transport-specific request context (e.g. starlette Request for HTTP
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# transports, None for stdio). Typed as Any because the server layer is
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# transport-agnostic.
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request_context: Any = None
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# Callback to close SSE stream for the current request without terminating
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close_sse_stream: CloseSSEStreamCallback | None = None
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# Callback to close the standalone GET SSE stream (for unsolicited notifications)
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close_standalone_sse_stream: CloseSSEStreamCallback | None = None
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# Callback the dispatcher runs when this request settles without a response
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# (e.g. it was cancelled), for a transport whose wire must still end the
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# request even though no response is written.
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on_request_unanswered: Callable[[], Awaitable[None]] | None = None
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# The transport's verdict on whether this message's request-scoped channel
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# can deliver a server-initiated request (see
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# `TransportContext.can_send_request`); a transport that says nothing leaves
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# it True.
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can_send_request: bool = True
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MessageMetadata = ClientMessageMetadata | ServerMessageMetadata | None
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@dataclass
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class SessionMessage:
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"""A message with specific metadata for transport-specific features."""
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message: JSONRPCMessage
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metadata: MessageMetadata = None
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